Background of the Invention
This invention relates to the treatment of industrial gas streams. More specifically, the invention relates to the treatment of industrial gas streams, such as a gas stream produced in a rendering process, to remove odorous and noxious component through the use of a gas scrubber system and to reduce biological fouling through the use of a biocide in the gas scrubber system.
Description of Related Art
In the processing of poultry, beef, fish, or other food, as well as in secondary processing (e.g., rendering), a large volume of organic material is processed that can generate large quantities of odiferous and noxious gases including organic sulfides, thiols, amines, alcohols, inorganic sulfides, ammonia, and simple carboxylic acids. These compounds are usually the result of biological action on the organic materials being processed. The odors produced are offensive and can travel significant distances to surrounding real estate. In other industries, such as chemical processing, paint production, wastewater treatment, etc., noxious compounds, such as volatile organic compounds (VOCs), are produced and are subject to environmental air quality regulations.
These gases are usually collected and sent to a scrubber system where they are removed from the gas phase. In such a scrubber system, the collected gases from the process are evacuated into a gas/liquid contactor where they are contacted by a liquid stream or scrubbing solution that is recirculated in the scrubber to absorb the odiferous and noxious gas compounds.
During operation of these scrubbing systems, the scrubbing solution will quickly saturate with the offensive gases and lose its absorbing potential. For example, as the scrubbing solution saturates with gases, particularly nitrogen-bearing gases (e.g., ammonia), the pH of the scrubbing solution will rise proportionally. This marked increase in pH reduces the solubility of the gases in the scrubbing solution and may cause them to flash to the atmosphere or off-gas. Further, at this point, the scrubbing solution has an intense disagreeable odor. Accordingly, additives may be added to the scrubbing solution to reduce its odor content. Ultimately, the scrubbing solution is either dumped to a wastewater treatment facility, or a portion of the scrubbing solution is sent to a wastewater facility and fresh makeup water is added to account for the difference.
In addition, as the water media recirculates in the system, there is an increase in the concentration of bacteria and protein and, accordingly, an increase in various types of biological growth, including the growth of bacteria, fungus, or yeast. This biological growth is typically referred to as biological fouling or biofouling and can cause problems within the system. For example, biofouling in the scrubber may begin to plug any packing used in the scrubber resulting in the obstruction of the flow of both the gas and liquid through the packing. This increases the pressure drop in the scrubber, and increases the gas flow rate through the scrubber thereby reducing the overall gas/liquid contact efficiency and removal efficiency of odorous and noxious components from the gas stream. Further, in those systems that utilize oxidizers to remove odorous and noxious components from the gas stream, the presence of biological activity and biofouling in the liquid streams will reduce the concentration of such oxidizers, thereby making less available for removal of the odorous and noxious components.
Accordingly, there exists a need in the art for a treatment process that has a sufficiently high electronegative potential to reduce substantially all odor and/or noxious compounds to simple, soluble, reduced-odor/noxious, or odor/noxious-free compounds and that reduces or prevents biofouling in the system. This treatment process would offer even greater advance in the art if the process could also eliminate or greatly reduce the high cost of treating the scrubber water effluent in the wastewater treatment process.